Your script attempts to decode every entry in CPPDEFINES as a tuple of (k,v). For defines like -DMY_MACRO=VALUE it works, you get ("MY_MACRO", "VALUE") as a result. Since you have however added -DCONFIG_SPIRAM_CACHE_WORKAROUND it will result in just the string "CONFIG_SPIRAM_CACHE_WORKAROUND ", which python cannot decode in (k,v). Thus it fails, which is correct.
Correct the script you have placed in
by taking care that CPPDEFINES may not only contain tuples. See e.g. Change name of firmware file - #10 by maxgerhardt.